Electric-snap-action switches



Oct. 8, 1957 T. D. e. WlNTLE ELECTRIC-SNAP-ACTION SWITCHES Filed 001:. 20, 1954 Attorney United States Patent @fiice 2,809,247 Patented Oct. 8, 1957 ELECTRIC-SNAP-ACTION SWITCHES Thomas D. G. Wintle, Hall Green, Birmingham, England,

assignor to J. A. Crabtree & Co. Limited, Walsall, England, a British company Application October 20, 1954, Serial No. 463,470

Claims priority, application Great Britain December 21, 1953 3 Claims. (Cl. 200-67) This invention comprises improvements in and relating to electric snap-action switches in which a bowed leaf spring of greater length than that between its supports, is adapted to be actuated with a snap-action over its deadcentre position.

The principal object of the invention is to provide an improved arrangement of compact construction composed of few parts adapted to be simply produced and having a long life and possessing efiicient electrical characteristics.

According to this invention the spring, of uniform thickness, is supported near its ends by a cradle, and bears between these ends on a member comprising a terminal to which it is secured, such member being adapted to permit flexing of the spring over the deadcentre position. The arrangement provides a narrow construction for facilitating side-by-side mounting of a number of switches in a restricted space, while riveting or welding which may be employed for securing the spring to said member provides an efiicient electrical joint avoiding the employment of bearing connections, such as are present with relatively moving parts. The flexing or snap-action of the spring is obtained by forming a bend, of somewhat semi-circular shape, between the terminal member and one end of the cradle. The improvements avoid the necessity for slitting or slotting the spring in order to impart resiliency, while any hardening of the metal due to variations in its thickness is also eliminated. The avoidance of sharply bent corners and of changes in section reduces the stresses on the metal, thereby increasing the life of the switch. Also the simple shaping of the spring permits relatively wide tolerances in production.

A moving contact button may be provided on one end of the spring while the other end is acted on by means such as a push button. The improvements enable the initial pressure on the spring for actuation of the switch, to enhance the engagement of the moving contact with its complementary fixed part, the pressure required to operate the switch being substantially the same as the contact pressure.

In order to enable the invention to be readily understood, reference will now be made to the accompanying drawing, illustrating by way of example one construction for carrying the invention into effect, in which drawing:

Figure l is a central vertical section showing the parts in one position.

Figure 2 is a side elevation with parts in section and showing the parts in the other position, and

Figure 3 is a plan of Figure 1 with the cover and push button removed.

Referring to the drawing, a narrow rectangular casing, moulded from insulating material, has a base through which extends three spaced terminal studs 2, 3, 4 on the upper end of one of which bears a stressed and bowed leaf spring 5, while the other pair are connected with fixed contacts 6, 7 either of which may be engaged with a moving contact 8 on the inner end of the leaf spring.

Each terminal stud is of hollow cup-like formation and is threaded externally to enable it to be secured in position by a nut 12 disposed within a recess in the casing. Each stud isalso internaly threaded for receiving a screw 9 which secures in position a bent terminal arm 10, having at its extremity a terminal screw 11. Through the upper end of the stud 4 extends a rivet 14 by which the spring 5 is secured. The upper surface of this stud is of part spherical shape 4a to permit the spring to flex thereon. The upper end of the stud 3 is shaped to enable the contact 7 to be secured thereon, while the upper end of the stud 2 is adapted for the mounting thereon of the contact arm 6 by means of a screw 2a. Instead of employing a nut 12 each stud may be formed witha plain exterior and riveted over for securing it in the base.

The spring 5 is of rectangular shape in plan and is formed near its inner end with a small rectangular slot 5a and at its outer end with cut-away portions 5b the slotting of such portions being adapted to be engaged by the hooked shaped ends of a rigid metal cradle or supporting member 13 disposed above the spring.

The cradle may be of reduced width at one end which is hooked at 13a for entry into the slot 5a in the spring, while its other end is bifurcated at 131) for hooked engagement with the lateral ends of the spring. The cradle is formed with a domed portion for imparting strength and for accommodating the head of the rivet in the position shown in Figure 2. Between the hooked ends a tongue portion 51: of the spring is engageable by a press button 15 mounted on a moulded cover 16 for the base. This button may be actuated by a spring blade 17 secured by rivets 18 to the cover.

The spring is bowed by forming it of semi-circular shape at 5d between its end support 14 and the bifurcated ends of the cradle. The other extremity of the spring beyond the cradle is provided with a silver button 8 constituting a moving contact, for engagement with the fixed contact 6 or 7 as shown in Figure 1 or Figure 2.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and described may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the appended claims.

Having thus described my invention, I claim:

1. An electric snap-action switch comprising a casing, a terminal disposed within said casing having a shaped bearing surface, a bowed leaf spring supported on said bearing surface at a point approximately midway of its length, said spring having a moving contact on its one end and actuating means operable on its other end, and a rigid cradle disposed parallel with and having its ends engageable at substantially the extremities of said spring, one end of said spring being provided with a slot and the other end with outer cut-away portions forming a tongue therebetween, said cradle having hooked ends for engagement with said slot and said cut-away portions of said spring, and actuating means operable on said tongue.

2. An electric snap-action switch comprising a casing terminal members mounted in said casing, a bowed leaf spring united to one of said members, said one member having a shaped bearing surface to permit flexing of said spring thereon, a rigid cradle having hooked ends for engagement with said spring, said spring extending beyond said cradle and having a moving contact on one end thereof, fixed contacts on the other of said terminal members engageable by said moving contact, said spring actuating means engageable with said tongue.

3. An electric snap action switch according'to clai'm2 in which the stud of each terminal is secured by a screw in a hollow cupped fiormation provided thercf9I.

V References-Cited ii the file of 'this' jaateht' U lTED STATES PATENTS.

LZQQSQ'S. Brocter May 14, 19.40.

4" r -Heikes "Apr. "17, 1945 Lees-Andrews Apr. 19, 1949 'Kaser N017, "1950 Bradley Feb. 16, 1954 FOREIGN PATENTS Great Britain May 12, 1941 

